Water Pump Kit with Housing – Fits Mercury/Mariner/Tohatsu 9.9-20 HP EFI (Replaces 8M0137849, 8M0135821)

$45.99 $73.00

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Water Pump Kit with Housing – Fits Mercury/Mariner/Tohatsu 9.9-20 HP EFI (Replaces 8M0137849, 8M0135821) is backordered and will ship as soon as it is back in stock.

Worry-free returns

You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.

Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This complete Water Pump Kit with Housing – Fits Mercury/Mariner/Tohatsu 9.9-20 HP EFI (Replaces 8M0137849, 8M0135821) provides everything needed for a full service of your lower unit's cooling system. It is designed for Mercury/Mariner 9.9–20 HP 4-Stroke EFI outboards (2013 and newer) and Tohatsu/Nissan MFS15E/MFS20E 4-Stroke models.

This kit is a direct replacement for Mercury part numbers 8M0137849, 98-8M0135821, 8M0134484, 46-8M0122064 and Tohatsu/Nissan numbers 3RS-87322-1 and 3RS-87322.

Installs in the lower unit to restore cooling performance.
Includes the housing, impeller, wear plate, and all necessary gaskets and seals.
Built with marine-grade neoprene, nylon, and stainless steel for durability in saltwater and freshwater environments.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
Mercury	8M0137849
Mercury	98-8M0135821
Mercury	8M0134484
Mercury	46-8M0122064
Tohatsu/Nissan	3RS-87322-1
Tohatsu/Nissan	3RS-87322

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury/Mariner models, this kit fits 9.9–20 HP 4-Stroke EFI outboards made in 2013 and later, with serial numbers 1R00814+ or 0R833820 and newer.

For Tohatsu/Nissan models, it fits MFS15E and MFS20E 4-Stroke outboards from 2013 and newer.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercury	9.9 HP EFI	9.9	4-Stroke	2013+	98-8M0135821	Serial 1R00814+
Mercury	10 HP EFI	10	4-Stroke	2013+	98-8M0135821	Serial 0R833820+
Mercury	15 HP EFI	15	4-Stroke	2013+	98-8M0135821	Serial 0R833820+
Mercury	20 HP EFI	20	4-Stroke	2013+	98-8M0135821	Serial 0R833820+
Mercury	9.9 HP EFI ProKicker	9.9	4-Stroke	2013+	98-8M0135821
Mercury	15 HP EFI ProKicker	15	4-Stroke	2013+	98-8M0135821
Mercury	20 HP EFI ProKicker	20	4-Stroke	2013+	98-8M0135821
Mercury	9.9 HP EFI SeaPro	9.9	4-Stroke	2013+	98-8M0135821
Mercury	15 HP EFI SeaPro	15	4-Stroke	2013+	98-8M0135821
Mercury	20 HP EFI SeaPro	20	4-Stroke	2013+	98-8M0135821
Tohatsu	MFS15E	15	4-Stroke	2013+	3RS-87322-1
Tohatsu	MFS20E	20	4-Stroke	2013+	3RS-87322-1
Nissan	MFS15E	15	4-Stroke	2013+	3RS-87322-1	Identical to Tohatsu models
Nissan	MFS20E	20	4-Stroke	2013+	3RS-87322-1	Identical to Tohatsu models

Technical Specs

Product Type: Water Pump Impeller Repair Kit with Housing
Installation: Lower Unit
Housing Material: Marine Grade Nylon
Housing Color: Black
Impeller Material: Marine Grade CR-Neoprene
Wear Plate Material: Marine Grade SS316 (Stainless Steel)
Warranty: 1 Year (aftermarket)

What’s in the Box

1 x Impeller (334-65021 / 3LD-65021)
1 x Housing
1 x Insert Cup
1 x Wear Plate
2 x Gaskets
1 x Key
1 x Seal Kit
1 x Installation Instructions

Installation Notes

Disconnect the battery and shift the outboard into neutral.
Remove the lower unit (gearcase) from the engine driveshaft housing. Typically, this involves removing 4-6 bolts.
Place the lower unit on a workbench and remove the bolts securing the water pump housing.
Slide the old housing, impeller, and wear plate off the driveshaft. Note the orientation of the old impeller vanes.
Clean the mounting surfaces and driveshaft, removing any old gasket material or sealant.
Slide the new wear plate and gasket onto the driveshaft.
Install the new impeller key into the driveshaft and slide the new impeller on, rotating it clockwise to seat the vanes correctly.
Install the new insert cup and place the new housing over the impeller assembly.
Lightly grease the bolts and tighten the housing down evenly.
Reinstall the lower unit, ensuring the water tube and shift shaft align correctly, and torque bolts to manufacturer specs.

Troubleshooting & FAQ

How do I confirm this kit fits my specific engine?

The most reliable method is to check your engine's serial number or model year. This kit is for Mercury/Mariner models 2013+ (with serials 1R00814+ or 0R833820+) and Tohatsu/Nissan MFS15E/MFS20E models 2013+. If your model or serial number is not listed, do not purchase.

What are the signs of a failing water pump?

Common symptoms include the engine overheating at idle or low speeds, a weak or non-existent "telltale" water stream from the engine, or a melted/deformed water pump housing upon inspection.

When should the water pump impeller be replaced?

As a preventative maintenance item, most manufacturers recommend replacing the impeller every 100-200 operating hours or at least once every season, regardless of hours used. This kit includes the housing, which should be replaced if the old one is warped, cracked, or heavily scored.

Is it necessary to replace the whole kit or just the impeller?

For a complete and reliable repair, replacing the entire kit—including the housing, wear plate, and seals—is highly recommended. These components wear together, and a worn housing or plate can cause a new impeller to fail prematurely.

What’s the difference between OEM and this aftermarket kit?

This is an aftermarket replacement part, not sourced from the original equipment manufacturer (OEM). It is engineered to meet or exceed OEM specifications for fit, material quality, and performance. All our parts are made in an ISO 9002 certified facility and undergo strict quality control.

How fast do you ship and what is the cost?

We ship worldwide quickly, with typical transit times of 5–15 days for most destinations. Standard shipping is free. If available for your region, expedited shipping options and costs will be presented at checkout.

What is the warranty and return policy?

This kit is covered by a 1-year warranty against manufacturing defects under normal operating conditions. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. See our official policy page or contact us for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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